content: /* Copyright (C) 2016-2018 Alibaba Group Holding Limited
  
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at
  
      http://www.apache.org/licenses/LICENSE-2.0
  
  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
  ==============================================================================*/
  
  // Protocol Buffers - Google's data interchange format
  // Copyright 2008 Google Inc.  All rights reserved.
  // https://developers.google.com/protocol-buffers/
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  //     * Redistributions of source code must retain the above copyright
  // notice, this list of conditions and the following disclaimer.
  //     * Redistributions in binary form must reproduce the above
  // copyright notice, this list of conditions and the following disclaimer
  // in the documentation and/or other materials provided with the
  // distribution.
  //     * Neither the name of Google Inc. nor the names of its
  // contributors may be used to endorse or promote products derived from
  // this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  package com.google.protobuf;
  
  import java.io.IOException;
  import java.nio.ByteBuffer;
  
  /**
   * Provides a number of unsafe byte operations to be used by advanced applications with high
   * performance requirements. These methods are referred to as "unsafe" due to the fact that they
   * potentially expose the backing buffer of a {@link ByteString} to the application.
   *
   * <p><strong>DISCLAIMER:</strong> The methods in this class should only be called if it is
   * guaranteed that the buffer backing the {@link ByteString} will never change! Mutation of a
   * {@link ByteString} can lead to unexpected and undesirable consequences in your application,
   * and will likely be difficult to debug. Proceed with caution!
   *
   * <p>This can have a number of significant side affects that have
   * spooky-action-at-a-distance-like behavior. In particular, if the bytes value changes out from
   * under a Protocol Buffer:
   * <ul>
   * <li>serialization may throw
   * <li>serialization may succeed but the wrong bytes may be written out
   * <li>messages are no longer threadsafe
   * <li>hashCode may be incorrect
   *   <ul>
   *   <li>can result in a permanent memory leak when used as a key in a long-lived HashMap
   *   <li> the semantics of many programs may be violated if this is the case
   *   </ul>
   * </ul>
   * Each of these issues will occur in parts of the code base that are entirely distinct from the
   * parts of the code base modifying the buffer. In fact, both parts of the code base may be correct
   * - it is the bridging with the unsafe operations that was in error!
   */
  @ExperimentalApi
  public final class UnsafeByteOperations {
    private UnsafeByteOperations() {}
  
    /**
     * An unsafe operation that returns a {@link ByteString} that is backed by the provided buffer.
     *
     * @param buffer the buffer to be wrapped
     * @return a {@link ByteString} backed by the provided buffer
     */
    public static ByteString unsafeWrap(byte[] buffer) {
      return ByteString.wrap(buffer);
    }
  
    /**
     * An unsafe operation that returns a {@link ByteString} that is backed by a subregion of the
     * provided buffer.
     *
     * @param buffer the buffer to be wrapped
     * @param offset the offset of the wrapped region
     * @param length the number of bytes of the wrapped region
     * @return a {@link ByteString} backed by the provided buffer
     */
    public static ByteString unsafeWrap(byte[] buffer, int offset, int length) {
      return ByteString.wrap(buffer, offset, length);
    }
  
    /**
     * An unsafe operation that returns a {@link ByteString} that is backed by the provided buffer.
     *
     * @param buffer the Java NIO buffer to be wrapped
     * @return a {@link ByteString} backed by the provided buffer
     */
    public static ByteString unsafeWrap(ByteBuffer buffer) {
      return ByteString.wrap(buffer);
    }
  
    /**
     * Writes the given {@link ByteString} to the provided {@link ByteOutput}. Calling this method may
     * result in multiple operations on the target {@link ByteOutput}
     * (i.e. for roped {@link ByteString}s).
     *
     * <p>This method exposes the internal backing buffer(s) of the {@link ByteString} to the {@link
     * ByteOutput} in order to avoid additional copying overhead. It would be possible for a malicious
     * {@link ByteOutput} to corrupt the {@link ByteString}. Use with caution!
     *
     * <p> NOTE: The {@link ByteOutput} <strong>MUST NOT</strong> modify the provided buffers. Doing
     * so may result in corrupted data, which would be difficult to debug.
     *
     * @param bytes the {@link ByteString} to be written
     * @param  output  the output to receive the bytes
     * @throws IOException  if an I/O error occurs
     */
    public static void unsafeWriteTo(ByteString bytes, ByteOutput output) throws IOException {
      bytes.writeTo(output);
    }
  
  }
  